Analyzing Lake Geneva from the air – a second wind for elemo

20.11.12 - One year after the MIR submersibles dove into the depths of Lake Geneva, the elemo program is delivering its first scientific results. And with the support of Ferring Pharmaceuticals, the operation will be extended with a campaign to make observations above the lake surface from a sensor-packed ultralight aircraft. The same experiments are planned above Lake Baikal in Russia.

In summer 2011, two Russian submersibles explored the depths of Lake Geneva as part of the scientific observation program elemo. Preliminary results are just now coming in. At the same time, EPFL and Ferring Pharmaceuticals, sponsor of the elemo program, are announcing a new installment of the exploration. This time, the scientists will make their observations from the air. Starting in late November, they’ll fly aboard ultralight planes to measure phenomena occurring at the interface between the air and water. Federal authorities have given their authorization for the flights. This scientific mission will be repeated over Lake Baikal in Russia.

On board the submersibles: preliminary resultsThe elemo program has already delivered preliminary results that have been extremely useful for assessing the health of the lake and for better protecting its ecosytem. Research is currently being done on pollution, the flow dynamics of currents, the bacterial fauna in the lake and the geology of the lake bottom.

Several scientific teams have already begun to publish research results; articles in peer-reviewed scientific journals should start to appear in the coming months and years. Data gathered from the MIR submersibles has enabled scientists to demonstrate a correlation between the presence of certain bacteria and heavy metals. They were also able to precisely measure how micropollutants – primarily pesticides or pharmaceuticals – spread throughout Lake Geneva from water treatment station outlets. (See press kit.)

Elemo takes to the airOn board their two ultralights, scientists from EPFL, Eawag and CEA (France) will study phenomena occurring near the surface of the lake, as well as the influence of air currents on the lake. Test flights will take place above the Lausanne and Nyon regions between November 26 and December 5, to test and calibrate the sensors. The official research campaign will begin in May 2013.

The scientists will use a “hyper-spectral” camera, a tool that allows them to decompose the light spectrum into hundreds of separate colors. From this, they can obtain an global image of certain elements close to the surface of the lake, such as bacteria, sediments, and dissolved gases. This kind of analysis is already done by satellites, but technical limitations (they can only separate a few parts of the light spectrum) and distance make many kinds of observations impossible.

At the same spot where the camera is pointed, a catamaran will simultaneously take water samples. By comparing the data taken from the air and from the water, the scientists hope to be able to develop new and better methods for analyzing the currents and the overall health of the lake.

For Michel Pettigrew, President of the Executive Board and Chief Operating Officer de Ferring Pharmaceuticals, a continuation of the company’s support of the program was self-evident. “Ferring has a keen interest in science and the environment and is especially committed to the Lake Geneva region. As a member of the local community, we are particularly proud to support the elemo project, which brings the best international scientific teams together with the objective of advancing our understanding the dynamics of Lake Geneva.”

As in the 2011 exploratory campaign on board the MIR submersibles, this extension of the elemo program will also continue in Russia, above the waters of Lake Baïkal – the world’s deepest lake – under the name “Project Léman-Baïkal.” By comparing results obtained in Switzerland and Russia, the scientists will be able to consolidate their knowledge and the methods they use to study lake environments.

Scientists on board MIR submersibles collected a huge amount of data on Lake Geneva, enough to keep their laboratories busy for many years to come. As we wait for the first scientific articles to be published, here is a brief overview of some preliminary results.

Analyzing pollution and micro-organisms

Tracing the path of pollutants and detecting them more easilyPresent in tiny amounts in the waters of the lake, micropollutants still manage to evade most modern filtration systems. Tamar Kohn and her EPFL team have gotten a better understanding of substances emitted by the Vidy water streatment station, and how these pollutants spread through the lake. They observed significant evidence of pesticides and pharmaceuticals near the outlet of the water treatment station. They were also able to determine the presence of micropollutants by making simple measurements of the electrical conductivity of the water. This method could prove to be a simpler and more direct way of monitoring water quality.

Resistant bacteria point to pollutionScientists from the University of Neuchâtel’s Microbiology Laboratory studied the impact of pollution, primarily heavy metals, on bacterial populations in the lake. Led by Pilar Junier, the research team concentrated on bacteria that form endospores, a dormant state that enables them to survive in a polluted area. The endospores make these bacteria excellent biological markers. Initial results indicate a correlation between the presence of endospores and heavy metal concentrations. New analyses should give further precision to this observation. This research also provides a better picture of which species survive best and will thus recolonize areas once the pollution disappears, and what to do to restore a healthy balance.

Bacteria play a role in depositing heavy metals on the lake bottomAssessing the ecological consequences of trace metal emissions in aquatic environments is very difficult. They are persistent; they don’t degrade over time and aren’t destroyed by human or biological processes. Once they have been introduced into aquatic ecosystems, they become involved in a number of chemical processes that are still not well understood. They take a number of different chemical forms. Mary-Lou Tercier-Waeber and Matthieu Masson from the University of Geneva’s CHIAM department took sediment samples from depths between 30m and 80m in the well-defined geographical zone of the Vidy bay, which is affected by micropollutants discharged by the Vidy water treatment station. The scientists observed that the concentrations of metals at the interface between the water and the bottom of the sediment is not correlated with the distance from the outlet of the treatment station, but rather to the bio-geochemical characteristics of the sediment. The highest concentrations were found in zones in which bacteria had colonized the sediment.

Geology and environmental history

Constantly changing canyonsAs the Rhone river flows into the waters of Lake Geneva, it carves out incredible underwater structures. These so-called “canyons,” some of which are 100m deeper than the lake bottom, were extensively analyzed by the MIR submersibles. Research by University of Geneva and Eawag scientists Stéphanie Girardclos and Flavio Anselmetti has already shown that the canyons are constantly in the process of changing in response to geological and climatic events. In particular, a thick layer of sediment observed at the outlet of the main canyon is evidence of a recent underwater landslide, probably following a major flooding event in the Rhone river in 2000.

Characterizing the lakebedPillows, wavelets and plains; trenches, mattresses and depressions: for fifty years already, the landscapes on the bottom of Lake Geneva have been classified into these six categories. Nicolas Le Dantec, Yosef Akhtman, Ulrich Lemmin and D. Andrew Barry, scientists from EPFL’s Ecological Engineering and Topometry Laboratories, have refined these definitions as part of the elemo campaign. Cameras on board the MIR submersibles revealed intermediate variants. In addition, the large scope of the observations has made it possible to map the distribution of the various morphology types. These depend in part on the slope of the lakebed, and possibly also on other parameters such as the activity of certain fish and bacteria.

Bacteria tell a taleThe chemical and biological composition of the soil in a given ecosystem reveals much about its history. Starting from this principle, Pilar Junier and her team from the University of Neuchâtel’s Microbiology Laboratory conducted a study to explore Lake Geneva’s past. They painstakingly analyzed the genetic material in sediment samples taken from the Rhone delta. They specifically observed the evolution of the number and nature of bacteria that form endospores. These organisms can go into a dormant stage if environmental conditions are unfavorable. They thus make very interesting markers, because variations in their concentration and state at different depths reflect changes in the chemical or microbiological equilibrium that occurred over time.

Geotechnical properties of lake sedimentsA team from EPFL and the University of Bremen looked at the geotechnical properties of the sediments on the bottom of Lake Geneva. Using Nimrod, a “dynamic penetrometer,” they developed a precise map of sediment transport in the lakebed at the Rhone delta and the Vidy bay. This device, piloted from inside the submersible, is a free-falling cylinder with pressure sensors on the bottom. These sensors measure the soil resistance along a vertical profile as the device penetrates the sediment. The team mapped the points measured and have already been able to observe that the sediment resistance is higher at the mouth of the Rhone and its channel into the lake than in other areas.

Methane flows from the depths to the atmosphereMethane is a greenhouse gas produced by the fermentation of organic material. It has a larger impact on global warming than CO2. In lakes, methane is formed by bacterial fermentation in the sediment on the lake bottom, and when the soil on the lakebed can no longer resist the pressure of the gas, methane bubbles suddenly rise through the water and into the atmosphere. Preliminary studies have shown large methane emissions in the Rhone delta. During the elemo campaign’s underwater expeditions, researchers from EPFL, Eawag, ETH Zurich and other Swiss, German and Canadian universities probed the canyons of Lake Geneva, collecting sediment cores and water samples from the depths in order to determine the quantity of methane being produced on the lakebed and the amount that escapes into the atmosphere. Preliminary results show that methane emissions vary depending on the lakebed topography and the amount of sediment transported into the canyons by tributaries.